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Camera Focus Points

Blurry Bears - Incorrect auto-focus point

Do you ever get pictures and wonder why they are not in focus or what is in focus is not what you intended?

Besides the obvious that you don’t have your auto-focus on your camera turned on, there are two main causes for this.  Let’s explore each one separately.

Auto Focus Mode

Generally, there are two key options for this setting.  In the Canon world they are “One shot” and “AI Servo”.  In the Nikon world they are “Single-servo AF” and “Continuous-servo AF” respectively.

One Shot – Suited for still subjects.  The focus point is achieved and locked on when the shutter button is pressed halfway.  The camera will only focus once during this routine so if your subject moves at all during this time it is possible your shot will not be in focus.  When focus is achieved the focus point in your view finder will flash red (keep this in mind for our next item below). Remember, this setting is best for subjects that are NOT moving.  As soon as the subject moves, you will not be in focus unless you have let go of the shutter button and press again.

AI Servo – Suited for moving subjects.  This AF mode is ideal for moving subjects when the focusing distance keeps changing.  When you press the shutter button half way the subject will be focused continuously.  As the subject moves closer or away from you the camera tracks the subjects and predicts the focusing distance immediately before the picture is taken.  Keep in mind, it is “predicting” the focus distance and thus it won’t always be 100% accurate.

On some cameras you will find a third option.  “AI Focus” on the Canon and “Auto-servo AF” on the Nikon.  In this setting, the camera determines whether the subject is moving or not and will select between the either One Shot or AI Servo (Single-servo AF or Continuous-servo AF on the Nikon).  I would not recommend using this setting as you are asking the camera to do yet one more thing that YOU the photographer are capable of determining.  The camera doesn’t seem to pick either of the two options consistently and thus you’ll find you have more pictures out of focus.

Selecting the AF Point

Today’s cameras offer AF point selection and through the view finder you can see what the camera has selected to focus for you. These cameras came anywhere from 4 focus selection points (old Canon D30) to 45 points in the Canon 1DS Mark III.

Automatic AF Point Selection – the camera selects the AF point automatically to suit the shooting conditions.  Now the first question I have to ask is this.  How does the camera know the shooting conditions you are in?  I will use this selection when I’m shooting fast paced action in a rather uncluttered environment such as when I shot at the Freestyle Motocross.  Using this mode allowed the camera to lock onto the subject faster and with the appropriate depth of field I could just shoot away.

Manual AF Point Selection – Now one might wonder why, if you have 45 focus selection points, you would ever want to manually select just one?  While it is true that you are selecting one, the surrounding focus points can assist you in your focus selection.  By utilizing only one focus selection point you are able to push your way through the clutter and focus on exactly what you desire.

As you can see below, had the Automatic AF Point Selection been used, there would be a high possibility the camera would not have focused on the lions eyes but rather focused on the leaves in front of the lion, as the auto-focus selection can appear to be rather random on what it decides to focus on.  My guess would be the leaves.

Using Selective auto-focus point

Lions Eyes - Selective auto-focus point

While not great photos by themselves they demonstrate the need to use Manual AF Point Selection.

~RoTP Team

Rule of Thirds Photography Article End

2 responses to “Camera Focus Points”

  1. Fred says:

    Good piece on explaining the differences between the modes and how they can be used. Might I add one more? I often leave mine set to the center focus point, lock the focus and recompose. I find it faster than dialing through the various points on my Canon. This is especially easy for still subjects.

    I’ll also mention manual focus for when you need total control. Good for studio use. Sadly, many of today’s lenses and cameras come with flimsy focus rings and difficult to use focus screens, making this harder.

  2. Brandon Bolin says:

    Hey Fred, sorry for the very late reply. About your focus point comment, that is exactly what I like to do. Much faster than dialing though the menu! I do believe there is an article on RoTP about that technique.

    Thanks for stoping by and sharing 🙂

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